Version
As changes are made to any asset in the system, Cascade Server keeps track of the changes in separate copies of the asset called Versions. These are accessible through the Versions tab of any asset in the Home area.
Each version has a timestamp that allows the user to see when the change was made. This functionality is also available through a workflow trigger as well.
A version may be either previewed, which shows the user what the asset looked like at that point in time, or activated, which means that the current state of the asset takes on the content of the specified version.
The versioning system is similar to a multi-level undo whereby you can revert to a previous version at a later date.
Additional Notes
Activating a version does not wipe out the current version for an asset. The current version becomes versioned as well, allowing you to effectively "un-do" the activation.